This invention relates to section joints in supported section assemblies, specifically a joint design improvement to absorb significant deflections in mullion section supports while limiting mullion joint deflections to less than the deflections of the mullion section supports.
A typical curtain wall panel assembly in a multi-story building consists of multiple wall panels supported by a number of laterally spaced apart, generally vertical mullion assemblies comprising a series of mullion sections spliced together in an end-to-end arrangement. Typically, the mullion section lengths are approximately equal to the height between adjacent floors of the associated building. Each erected mullion section is typically secured or anchored near an edge of an adjoining floor slab or other building support element that supports the mullion assembly and the associated curtain wall panels. Some of the functions of the erected curtain wall system are to provide a pleasing appearance and to provide a long term weather shield for the building interior against wind, rain, temperature, and other weather conditions.
Since each of the mullion sections are typically supported or anchored at the floor edges, floor movement or other deflection (e.g., under differential live loads) typically causes a comparable movement of the supports/anchors, mullions, and the curtain wall assembly. These movements, especially differential movements of floor edges of greater than about xe2x85x9c inch or 1 cm, may adversely impact on the appearance of the curtain wall, disable the weather sealing functions, and could even cause structural failure of the curtain wall system and/or its components, such as the loss of panels and damage to the mullion assemblies.
The prior art solutions to this deflecting building floor and mullion support problem have included two design options. The first option is to design the curtain wall system to be structurally strong and/or compliant enough to absorb the differential inter-floor or other deflections. However, this option may lead to objectionable appearance, added cost, and/or long term weather shield performance problems, e.g., weather seals may not be able to reliably seal after repeated large joint compressions and expansions. The second option is to reduce the magnitude of the differential inter-floor deflection by stiffening the building floor supports/anchors. However, this option may not be feasible due to architectural limitations or treatment (e.g., a cantilevered floor slab design with thickness and material constraints) or may result in significant cost increases.
One embodiment of the present invention limits attached mullion section motion to within a tolerable range for a curtain wall assembly even when differential mullion support motions are outside the tolerable range. This is accomplished in an open gap embodiment by providing an open gap equal to or less than the tolerable range and prevent compressive relative displacement between mullion sections and allowing greater relative vertical displacements between a floor anchor and an adjoining mullion section. Thus, when floor deflections close the gap, further floor deflection causes an adjacent lower mullion section to provide support for the contacted upper mullion section that would otherwise move outside a tolerable range. Additional downward floor deflections beyond a tolerable range for the attached curtain wall assembly are allowed by a mullion support slot and a slidable connection. Thus, the adjacent floor continues moving downward and no longer supports the previously supported mullion section which is now supported by the lower mullion section.
In a preferred limited-gap embodiment, the splice gap between mullion sections may exceed the tolerable motion of the associated curtain wall panels, but a gap-limiting means is provided in addition to a slidable support. The gap-limiting means also provides support for a displaced mullion section (that would otherwise be displaced outside the tolerable range if supported by a displaced proximate floor anchor) by hanging on an above mullion section and/or being supported from a lower mullion section, allowing the dead weight of the supported mullion section(s) to be split among several other mullion sections and their associated supporting hardware. The preferred splice gap-limiting means comprises a gap containing a weather seal and a splice gap-limiting slot and sliding bolt connector where the gap-limiting bolt and slot limits relative up or down motions between mullion sections to acceptable levels for the curtain wall and weather seal. The preferred mullion support and joint assembly also includes a bearing support plate that can be field positioned using self-tapping screws avoiding the need for field drilling and/or welding.